Like much of the rest of the travel industry, online travel bookings in 2009 took a hit. Spending by consumers dipped for the first time in recent memory, from $112.9 billion in 2008 to $104.3 billion in 2009 (down 7.6%), according to a report from research firm Forrester.

However, while online bookings for virtually every segment slipped — including air travel by a punishing 7.7% to $61.8 billion (can you say, “Hello, baggage fees“?) — online car rentals fared relatively well, sliding only 2.1%, to $12.1 billion.

By comparison, hotels tumbled a staggering 9.9%, to $28.6 billion. Cruise bookings were down a modest 3.4%, to $1.1 billion. Tours were flat, but at just over $600 million, it remains a tiny sector.

Why did online car rentals hold up?
In large part, online car rentals can thank the fact that gasoline prices moderated somewhat in 2009. Cash-strapped consumers still stricken with wanderlust had good reason to hop back in their car to take trips.Gasoline prices averaged $2.03 per gallon in late March 2009, for instance – significantly down from $3.26 per gallon in late March 2008, according to the Energy Information Administration. Currently, a gallon of gasoline sells for about $2.79 per gallon, on average — still down from those spasming numbers seen on spring of 2008 but helping to explain why online car rentals are not accelerating faster.

Fortunately for each segment of the travel industry, the outlook for online travel bookings is looking good, thanks in part to the (slowly) improving economy. In fact, Forrester is projecting that overall online bookings will trend up an average 8.1% each year from 2009 to 2014, when consumers will spend more than $153 billion booking travel online. Airfare will still be the lion’s share of online bookings, though hotels will take a small bite out of that stranglehold, as evidenced by the pie charts below.